The present invention relates to a method for maintaining the freshness, and particularly the color, of meat, fish or processed foods made from meat or fish, and to a method for promoting the growth of animals for the production of meat.
Meat of livestock and some fish are of a bright red color when fresh, but the color changes to brown or gray with time. Thus, discoloration of meat is an important indication of aging, and consumers usually select meat or fish based on color as a guide to quality. Japanese consumers pay in particular attention to the color of raw fish because they often serve it in a raw state. They also pay much attention to the color of raw meat. The discoloration of meat and fish is predominantly caused by oxidation of haem pigments. The haem pigments contained in meat include myoglobin in myofibril and hemoglobin in erythrocytes of residual blood. It has been attempted to maintain the color of meat, fish, and processed foods made of meat or fish by the use of additives, but the use of additives in the past has been insufficiently effective or has had safety problems.
Aging of meat is indicated by the following phenomena :(1) fading caused by oxidation of haem pigments, (2) spoilage by oxidation of lipids, (3) rotting by microorganisms, (4) losses by dripping and (5) changes in texture. Various methods for suppressing aging of meat have been investigated. Particularly, in recent years, purchases of food have been decreasing in quantity due to smaller families, and furthermore people desire faster and simpler cooking. Accordingly, it is becoming more common for meat or fish to be sold in small packs and in the form of slices, but sliced meat is more susceptible to aging, particularly fading, than is a block of meat. Thus, the need exists for an effective method for suppressing aging of meat, fish and processed foods, thereby maintaining the freshness thereof.
One known method for preventing aging of meat, for example, is to prevent oxidation of oils and fats contained in meat or fish by using an antioxidant to suppress spoilage caused by lipid oxidation. Vitamin C, natural vitamin E, and erythorbic acid can be used as an antioxidant for fresh meat or fish in Japan, but they are not sufficient to maintain freshness, particularly color. Also, antioxidants such as butylhydroxy toluene (BHT) and butylhydroxy anisole (BHA) have been used for oils and fats used in processing, but it was reported that BHT and BHA are carcinogenic (Ito et. al J. Matl. Cancer Inst. 70, 343) and their use is prohibited by administrative guidance.
Also, ascorbic acid (vitamin C) and polyphosphoric acid are widely used in order to improve color, water content and texture of meat, fish, and processed foods made from meat or fish, particularly preserved meat. However, vitamin C is apt to interact with Fe in meat to change the color of meat, i.e., to cause browning, and excess intake of polyphosphoric acid results in abnormalities in bones. Therefore, they are not desirable as additives for safe foods.
Additionally, it is rather difficult to let an additive penetrate into a large block of fresh meat or preserved meat. Therefore an additive useful as a feed additive to maintain the quality of meat would be desirable, but such an additive has not been developed successfully.
As mentioned above, an additive for suppressing aging and maintaining freshness of meat which is effective and safe has not been known, and there has not been an additive which does not treat meat directly and is added to a feed to maintain the quality of meat. Also, a feed additive which is effective for maintaining the quality of meat and can promote the growth of animals was not known.